Signaling system



Aug. 31, 1937. F. K. Low

SIGNALING SYSTEM Filed June 22, 1935 INVENTOR 5y l-i/(LOW ATTORNEY;

Patented Aug. 31, 1937 UNITED STATES PATENT OFFICE Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation of New York Application June 22,

9 Claims.

This invention relates to signaling systems and particularly to signaling systems comprising an electrical signaling circuit.

The object of the invention is to provide a more sensitive signal receiving means and to insure the accurate response of such a means to incoming signals.

This invention is a signal receiving means comprising an impulse relay, a transformer and a three-element ionic tube, primary windings of the impulse relay and transformer being con nected in series with a line to respond to the opening and closing of the line by the operation of a signal sender. The secondary winding of I 1 the transformer is connected to the grid element of the tube so that the opening of the signaling circuit effects the breakdown of the tube and the temporary energization of the secondary winding of the relay by the discharge of a condenser in a direction to hold the relay operated for a short interval. Upon the condenser being sufiiciently discharged, it is effective to deenergize the tube and the charging of the condenser through the secondary winding of the relay is thereupon effective to aid the release of the signal receiving relay.

A better and more complete understanding of the invention may be obtained byccnsidering the specific embodiments of the invention shown in the drawing which forms a part of this specificationl The invention is not, however, limited in its application to these specific arrangements and isjin general, applicable to any signaling system in which selective signals are created by the opening and closing oi a signaling circuit.

* Referring to Figs. 1 and 2 of the drawing, IR represents impulse receiving means in an automatic telephone ofiice for operative connection to any one of a plurality ofxsubscribers lines. In Fig. 1 the line H connects the individual subscrlbers station A to the central oflice and in Fig. 2 the line 3! is used as an outgoing one-way trunk from a private branch exchange, P. B. X., to the central oflice. Fig. 3 of the drawing shows a a set of graphs which facilitate the description of the arrangements shown in Figs. 1 and 2.

The apparatus at station'A includes a dial HI, and the apparatus at the private branch exchange includes an operator's dial 30, or other I. equivalent impulse sender, each for use in transmitting dial impulses. The central office includes automatic switching equipment (not shown) for establishing a connection between a calling line and an idle impulse receiving means ll IR. The impulse receiving means IR may be 1935, Serial No. 27,940

used to directly control in succession each of a train of selective switches to complete a desired connection or may be used to operate a register which thereafter controls the various switches through which a desired connection is established. Reference may be had to chapter III of the second edition of Automatic Telephony by Smith and Campbell for a description of an automatic telephone system comprising switches of the well-known Strowger type controlled by the dial impulses when dialed. Reference may be had to Patent No. 1,395,977, granted toF. A. Steam et al.,-November 1, 1921 for a description of a system comprising switches of the powerdriven panel type which are revertively controlled by a register-controller, set in accordance with trains of impulses created by the operation of the dial at any calling subscribers station to which the 'registercontroller is connected.

The impulse receiving means IR, shown in Fig.

1, of the drawing, comprises a transformer l3, a

polarized impulse relay IS, a slow-to-release relay il, condensers 20 and 2|, a three-element gasfilled tube 22, and a register or selector 21. The polarized relay l6 has three windings, the upper winding for connection in series with a calling line, the middle winding for biasing the contacts in the position shown in the drawing, and the lower winding for insuring the response of relay 16 to each impulse of a series received'by the upper winding. The tube 22 is filled to a low pressure with a gas, such as neon, argon or helium. Although shown as having a cathode which is heated indirectly, the tube may be one in which the cathode is directly heated. For a complete description of hot-cathode three-element gasfilled tubes, reference may be had to an article entitled Hot-cathode thyratrons by A. W. Hull, published in General Electric Review, volume 32, pages 213 to 223, inclusive.

The resistor I9 and condenser 20 form a filter forpreventing dial tone or disturbances other than those legitimately created by the dial from affecting the control and operation of tube 22. The condenser l4 and resistor l5 form a surge filter which aids in the suppression of such disturbances. With the receiver removed from the receiver hook at station A to originate a call and the line H connected to the impulse receiving means IR, the ringing condenser 9 is bridged across the conductors oi. line H in parallel with the transmitter; and the condenser 9 is, therefore, partially charged. As soon as the dial is moved oiT-normal, the transmitter and condenser are short-clrcuited so that the condenser is discharged. While the dial is restoring to normal, the condenser is charged each time the dialing loop is opened and discharged each time the loop is closed. Each time the dialing loop is opened at the dial contacts the current drops abruptly, the condenser charging current being built up slowly due to the high impedance of the ringer which is in series with the condenser. The result is that the current through the upper winding of impulse relay l6 drops sharply, then rises due to the condenser charging current, and then again decreases; and relay l6 may, unless otherwise prevented, release, reoperate falsely and again release. Such a condenser charging current will herein be referred ,to as "subset surge. If the line H is connected to a private branch exchange as is the line 3| in Fig. 2, the moving of the operator's dial 30 out of normal position causes the operation of relay '28, thereby'short-circuiting the retard coil 29 which is bridged across the conductors of the line 3| upon insertion of the. plug P in the jack to which the line is connected. When the dial reaches normal, after transmitting a series of impulses, the retard coil 29 is again inserted in the dialing loop and, unless otherwise prevented, the impulse relay may release. the current, due to the insertion of the retard coil in the dialing loop, will hereinafter be re-. ferred to as a P. B. X. surge; While the filter unit I l-l5 might be large enough to entirely prevent false operation of the impulse relay due to subset surges, such a filter would also have a tendency to cause bell-tapping at the subscribers 3 station. The filter |4|5 is,- therefore, one

which is only partially eifect'ive in eliminating false operation due to subset and P. B. X. surges; and the transformer l3 and ionic tube 22 are provided, in' combination with the-lower winding of relay IE, to completely eliminate such false operation in the manner hereinafter described.

The lower winding of relay I6 is normally connected in a circuit from battery through resistor 23, condenser 2|, lower winding of relay l6, retard coil' 25 and resistor 26 to ground. Condenser 2| is, therefore, normally charged; and, since the anode of tube 22 is permanently connected to the junction point between coil 25 and V the lower winding of relay I6, there is normally a diiference in potential across the cathode and anode equal to the battery voltage. Although the grid of tube 22 is normally at the same potential as the cathode, the tube does not ener- 8126 since the filamentv circuit is not closed. Condenser 20 is normally not charged. Upon extension of a calling line II to the impulse receiving means IR, ground potential is connected 7 V to the impulse receiving means to complete a the filament and cathode of tube 22 and to complete a circuit through resistor l8 for energizing the middle winding of relay l6 so as to bias the contacts of this relay. With the filament circuit closed, there is a drop in potential in resistor 23, so that the potential of the cathode is increased, making the grid sufliciently negative with respect to the cathode to prevent energization of the tube. The drop in potential in resistor 23 also causes condenser 20 to be slightly charged. The drop in potential in resistor 24' is high so that condenser 2| is only slightly discharged and the potential difierence across the cathode and anode only slightly decreased. The

75 electromotive force induced in the secondary Such adrop in circuit through resistors 23 and 24 for heatin winding of transformer l3, upon closure of the impulse circuit through the upper winding of relay l6, merely serves to decrease the potential of the grid; that is, the negative bias of the grid with respect to the cathode is increased so that the tube remains deenergized. I

With relay l6 operated, a circuit is closed for operating the slow-to-release relay H. No further action occurs until the subscriber at station A operates the dial ill to secure connection with any other desired station. The opening of the impulse circuit to transmit the first impulse of a series causes the deenergization of the upper winding of relay l6 and induces an electromotive force in. the secondary winding oftransformer l3 which renders the grid element of tube 22 positive-with respect to the cathode, thereby causing the ionization of the gas, and energization of the tube. The potential of the anode of tube 22 is thus decreased by the amount of the potential drop in coil 25 and resistor 26 so as to be only a'few volts higher than the cathode; and the condenser 2| discharges through the lower winding of relay I6. The combined impedance of coil 25 and resistor 26 bein high in comparison with the impedance of the lower winding of relay |8, the cathode-anode current through the relay winding is larger than that through coil 25; and the energization of the lower winding of relay l6, due to the discharge of condenser 2|, is in the operating direction so as to temporarily hold relay l6 operated. As soon as condenser 2| is discharged, the path through the condenser and lower winding of rei lay. I6 begins to act as a shunt across the cathode-anode of the tube, and condenser 2| again begins to charge. The impedance of the con- 7 denser and relay winding being low as compared.

with the cathode-anode impedance, the tube is thereby deenergized, such use. of a condenser shunt for extinguishing anionic tube being well lrnown in the art. After the tube is extinguished, condenser 2| continues to charge, the

charging current being effective to energize the lower winding of relay IS in a direction to aid the release of relay I6. The charging of condenser 2| proceeds at a rate which is determined by the impedances of the retard coil and resistor 26. The release of relay l6 closes the cir-' cuit for operating the register or selector 21.

no eflect on tube 22; and relay I6 remains operated until the impulse circuit is opened to trans- ,mit the next succeeding impulse of the series.

Thereupon the above dacribed cycle of operation is repeated, the energization of. the lower winding of relay l6 by the condenser discharge current being efiective to hold relay |6 operated, in case the closed period between succeeding dial impulses is too short. Being slow in releasing, relay. l'l remains operated during dialing.

Tomore fully appreciate the eifect of the lower winding of relay I6, reference may be had to the graphs shown in Fig. 3. The curves 50, 53 and 55 represent, respectively, the magnetic flux resulting from the energization of the upper winding. the lower winding, and both windings comings separately and together when the upper winding is connected in serieswith a line of such a character as to impose a severe operate condition, for instance, one in which the line is of high resistance and lower capacity and in which there is a minimum closure of the impulse circuit between succeeding dial impulses of a series.

The curves 10, 13 and 15 represent, respectively, the magnetic flux resulting from the energization of these windings separately and together when the line is used as a P. B. X. trunkand a retard coil is bridged across its conductors as a holding bridge. Points directly above or below each other in each set of curves represent simultaneously existing conditions and are given the same reference character. The dotted horizontal lines running through curves 50, 60 and I and through curves 55, 65 and 15 represent the level of flux required to just balance out the flux of the biasing, middle, winding of relay It. The resultant flux of the upper and lower windings must be greater than this level to operate or hold relay l6 and less than this value to cause release of relay IS.

The opening of the impulse circuit through the upper winding of relay I6 occurs at point of curves 50, 53 and 55, the flux due to the upper winding, taking a substantially vertical drop at this time. The flux due to the upper winding alone, after being reduced sufiiciently to permit release of relay l5, again increases while the line and the subset condensers are being charged, the increase in flux being sufficient to cause a false reoperation of relay I6 if not otherwise prevented. coincidental with the substantially vertical drop in flux due to the upper winding, is a substantially vertical building up of flux due to the condenser discharge current in the lower winding as shown by curve 53; this flux starts to decrease as the discharge current becomes smaller and at point 54 begins to decrease at a faster rate due to the deionization of the tube and the. recharging of the condenser, the flux being reversed as indicated by the portion of the curve below the horizontal axis. The resultant flux is shown by curve 55 to decrease at a moderate rate upon the opening of the impulse circuit but not enough to permit relay It to release before the subset surge has ceased, and to decrease more rapidly after the tube 22 is deenergized and condenser 2| is being recharged. Relay I 5 begins to release at point 56.

I which the flux in the upper winding begins to build up due to the reclosing of the impulse cir-.

cuit at the end of the dial impulse, relay I! start ing to reoperate at point 51. These curves clearly show that the flux produced by the lower winding of relay I5 is not only eifective'to prevent the false release and reoperation of relay l6, due to a subset surge, but is also effective to bring about- Point 52 represents the time at the dial contact openings are of relatively short duration.

Referring to curves 60, 63 and 85, point 8| represents the time at which the flux in the upper winding of relay I 5 begins to build up due to the closing of the impulse circuit at the end of an impulse, and point 82, represents the time at which this flux decreases vertically due to the opening of the-impulse circuit to transmit the next succeeding impulse of the series; the time the impulse circuit is closed is so short that the next, impulse would fail to be registered, except for the building up of the flux due to the energization of the lower winding by the discharge of condenser 21.45" represented by curve 63. The resultant flux, as shown by curve 65, shows that relay (6' is held operated by the energization of its lower winding, after the opening of the impulse circuit. At point 64, the condenser 2| starts relay IS drops sufficiently, as shown in curve 10,

to permit the impulse relay to release; but the condenser discharge current in the lower winding builds up a flux as shown in curve 13. Curve shows the resultant flux which is effective to prevent the release of the impulse relay.

The impulse receiving means IR, shown in Fig. 2 of the drawing',.comprises the filter 34, 35, transformer 33, three-element cold-cathode gasfilled tube 42, filter 39-40, resistor 43, polarized impulse relay 35, slow-to-release relay 31, and

- register or selector 41. The arrangement'is sub-' stantially the same as that shown in Fig. 1 except that a cold-cathode tube is used instead of a hot-cathode tube. For a description of a coldcathode tube suitable for use in this arrangement, reference may be had to Patent No. 1,784,869 granted to F. Gray, December l6, 1930. The operation of the arrangement of Fig. 2 is the same as that above described.

What is claimed is: i

1. In a signaling system, a line, a signal sender, a signal receiving relay, a transformer, a signaling circuit including said line and sender and primary windings of said relay and transformer, an ionic tube, and means including said tube and secondary windings of said relay and transformer effective in response tothe opening of said circuit for holding saidrelayoperated for a short interyal of time.

2. Inc. signaling system, aline, a. signal sender, a'- signal receiving relay, a transformer, a signaling circuit including said line and sender and primary windings of said relay and transformer,

an ionic' tube, and means including said tube and secondary windings of said relay and transformer,

. said means being operatively non-responsive to the closing of said circuit and operatively responsive to the opening of said circuitfor holding said relay operated for a short interval of time.

3. In a signaling system, a line, a signal sender,

, a signal receiving relay, a transformer, a signaling circuit including said line and sender and primary windings of said relay and transformer, an ionic tube, and means including said tube and secondary windings of said relay and transformer effective in response tothe opening of said circuit for aiding the release of said relay.

4. Inc. signaling system, a line, a signal sender,

a signal receiving relay, a transformer, a signaling circuit including said line and sender and primary windings of said relay and transformer, an ionic tube, means including said tube and secondary windings of said relay and transformer effective in response to the opening of said circuit for holding said relay operated for a short interval of time and for thereupon aiding the release of said relay. 5. In a signaling system, a line, a signal sender, a relay, a transformer, a three-element ionic'tube, -'a first circuit including a first winding of said relay'and one winding of said transformer and said line and said signal sender all in series, a

register operatively controlled by said relay in response to impulses created in said first circuit by the operation of said sender, a second circuit including a second winding of said relay, the current in said second circuit being efiective to energize said second winding in electromagnetic opposition to the energization of said first winding by the current in said first circuit, means comprising another winding of said transformer for varying the potential of the control element of said tube to cause energization of the tube upon the opening of said first circuit, and means comprising a capacitor, an inductor and a third winding of said relay connected to the anode of said tube, said last-mentioned means being effective upon energization of the tube to hold said relay operated for a short interval of time, to 'deenergize the tube, and to aid the release of said relay all in the order recited.

6. In a signaling system, a line, a retard coil at one end of said line, an impulse dial having impulse contacts connected in series with said coil and line, means effective while said dial is 0&- normal for short-circuiting said coil, a transformer and an impulse relay at the other end of said line, a circuit including said coil, impulse contacts, line, a primary winding of said transformer, and a primary winding of said relay for operating said relay, an ionic tube, and means including said tube and secondary windings of said transformer and relay for preventing the release of said relay upon opening of the short circuit around said coil when said dial reaches normal.

7. In a signaling system, a line, a signal sender,

a signal receiving relay, a transformer, a signal-' for operating said register closed by said relay at the beginning of each impulse and opened by said relay at the end of each impulse, and means comprising a transformer and a three element ionic tube for delaying the response of said relay at the beginning of an impulse and for aiding the response of said relay at the end of an impulse.

9. In a signaling system. according to claim 8, a retard coil normally connected in series with the impulse contacts of said sender, and relay means effective during the creation of a. series of impulses for short-circuiting said coil, said transformer and ionic tube being efiective upon opening of said short circuit to prevent the response of said impulse receiving relay.

" FaANK K. LOW.

-tion of said sender, an impulse register, a circuit 

